This description relates to subsea boosting, more particularly, to systems and methods for subsea boosting in high-voltage direct current (HVDC) and/or high-voltage alternating current (HVAC) transmission and distribution systems.
As oil and gas fields in shallow waters diminish, producers are tapping offshore fields in deeper waters with oil installations that operate far below the surface of the sea. The typical equipment for such subsea oil recovery and production include gas compressors and various pumps for multiple functions. Electric variable speed drive (VSD) and motor systems are one way to power such equipment directly under the deep water. Therefore, the delivery of electric power from a remote onshore utility grid or power generation is important to secure a reliable production and processing of oil and gas in subsea locations. Typically, the transmission power requirement is up to several hundred megawatts for medium to large oil/gas fields.
Alternating current (AC) transmission and distribution systems are one technology suited for delivery of power to subsea locations. Such systems typically deliver AC power from a platform or onshore location to a large subsea transformer through a large power cable. Power is transferred from the subsea transformer to subsea AC switchgear through another power cable. The subsea AC switchgear feeds AC power to one or more subsea VSDs via yet another cable. The VSDs each provide variable AC power to electric motors via a power cable. The connections between components in subsea AC distribution systems typically require wet mateable connectors, which are significantly more complex and expensive than dry mateable connectors. In addition, the power requirement and thus the size of components in subsea boosting systems has generally increased over time. Some known systems utilize three to five megavolt-ampere (MVA) pumps, each of which may weigh more than ten tons. Other components in known subsea boosting systems and/or AC transmission and distribution systems are also very large and/or heavy. Moreover, some AC transmission and distribution topologies face technical challenges, which become more significant when transmission distance is in excess of fifty kilometers.